A method of manufacturing reactive sputtered thin film by using a conventional facing-targets sputtering apparatus as disclosed in Japanese Laid-open Patent H2-38310. The method disclosed in this example is such that oxygen plasma is locally generated on the upper surface of a substrate, and then oxidation reaction occurs against particles sputtered from the target, thereby manufacturing an oxide superconductor film. FIG. 4 is a sectional outline drawing showing the configuration of an essential portion of a conventional opposed-target sputtering apparatus.
In FIG. 4, paired targets 4 are oppositely disposed at a spaced interval. At the backs of these targets 4 are respectively disposed magnets 3 for forming a magnetic field between paired targets 4. Substrate 5 is disposed in a direction perpendicular to the opposing direction of targets 4 and so as to face toward the space of the magnetic field formed by magnets 3 disposed at the backs of targets 4. Discharge gas inlet port 9 is disposed near the side of target 4. Argon gas as discharge gas is introduced from gas inlet port 9 into a vacuum chamber in which paired targets 4 are disposed. After introducing the gas, DC voltage from DC power source 8 is applied to paired targets 4, thereby generating plasma enclosed in the magnetic field.
Also, in the space between substrate 5 and shield cover 1, there is provided gas outlet port 6 for introducing oxygen gas as reaction gas. Further, electrode 7 connected to high-frequency power source 2 for generating plasma gas is disposed in outlet port 6. It is preferable to dispose gas outlet port 6 at the front or back side of electrode 7. These are arranged in vacuum chamber 10, and after forcing the air out of the vacuum chamber by means of a vacuum pump (not shown), plasma is generated by introducing discharge gas. Particles sputtered from targets 4 due to the plasma then generated react with plasma produced in the vicinity of electrode 7 disposed near substrate 5, and then, for example, an oxide thin film is formed on the surface of substrate 5.
In such a reactive sputtering apparatus using a conventional facing-targets sputtering system, electrode 7 connected to high-frequency power source 2 for generating reaction gas plasma is disposed in the vicinity of substrate 5. Accordingly, substrate 5 is exposed to plasma with a high electron temperature, and the thin film formed on the surface of substrate 5 is damaged by plasma while the film is formed. Further, since substrate 5 is heated by plasma, there is a problem that the thin film cannot be formed at a desired temperature of the substrate.
To cope with such a problem, disclosed in Japanese Laid-open Patent H6-252098 is an apparatus for executing surface treatment by applying an activated neutral particle beam to the substrate. A high-density neutral particle beam is produced from a high-density ion beam, and the neutral particle beam enables surface treatment at a higher speed. FIG. 5 is a sectional outline drawing of the plasma source.
The plasma source comprises plasma chamber 15, after-glow transport chamber 18 and treating chamber 24. That is, plasma 100 is generated by discharging gas in plasma chamber 15. In after-glow transport chamber 18, plasma 100 is taken out as after-glow, and also, while plasma after-glow 102 is transported, ions contained therein are neutralized to make neutral particles. In treating chamber 24, the neutral particles produced in after-glow transport chamber 18 are introduced for executing surface treatment of substrate 25. In this configuration, only neutral particles are applied to substrate 25, and it is possible to execute surface treatment without charge-up even if the object to be treated is a nonconductor.
A specific configuration of the plasma source will be described in the following.
Plasma chamber 15 is able to generate microwave plasma by using electron cyclotron resonance (ECR). That is, ECR electromagnet 11 is disposed at the outer periphery of plasma chamber 15, and microwaves transmitted by wave guide 13 are introduced through window 12. Also, first gas guide 14 is disposed in plasma chamber 15, and discharge gas is supplied from first gas guide 14.
Opening 16 is provided at the boundary position between plasma chamber 15 and after-glow transport chamber 18, and plasma 100 generated in plasma chamber 15 is taken out as plasma after-glow 102 into after-glow transport chamber 18 through opening 16.
At after-glow transport chamber 18, magnetic field shaping electromagnet 17 is wound on the outer periphery thereof. Thus, static magnetic field 104 is formed in the direction from plasma chamber 15 to treating chamber 24. Also, at the inner periphery of after-glow transport chamber 18 is disposed a ring-shaped gas outlet port 19, and the charge-exchange gas supplied from second gas feeding pipe 20 is supplied from gas outlet 19 to plasma after-glow 102.
Accordingly, plasma after-glow 102 is transported in the direction of treating chamber 24 with its diameter restricted to a specific shape by static magnetic field 104. In this way, positive ions contained in plasma after-glow 102 turn into an ion beam with its sputtering direction controlled. The ion beam is neutralized due to charge-exchange reaction with the charge-exchange gas during the process. As a result, a neutral particle beam having the same sputtering direction is formed. At this stage, electrons and negative ions or positive ions are remaining in the neutral particle beam.
At the boundary position between after-glow transport chamber 18 and treating chamber 24, there are provided electron repulsion electrode 21 and ion repulsion electrode 22 disposed adjacent to each other. Electrons and negative ions remaining in the neutral particle beam are repulsively removed by electron repulsion electrode 21. On the other hand, positive ions having passed electron repulsion electrode 21 are repulsively removed by ion repulsion electrode 22. Consequently, only neutral particle beam 106 is introduced into treating chamber 24.
Treating chamber 24 can be exhausted desired vacuum level by means of a vacuum pump (not shown) connected to exhaust port 23. Also, substrate holder 26 is disposed therein, and substrate 25 is fitted to substrate holder 26.
However, when such a plasma source is used as a plasma source for reaction shown in FIG. 4, there are problems as mentioned in the following. That is, neutral particle beam 106 thus formed is not uniform in its diametric direction, and a thin film formed by neutral particle beam 106 through reaction is liable to become non-uniform in its film quality and in-plane distribution of film thickness. Also, neutral particle beam 106 is sometimes sputtered toward the targets and reacts with the target material, causing a compound to be produced on the target surface. As a result, arc discharge is generated at the surface of the target during the sputtering operation, and there may arise generation of unstable sputtering and also splash in the thin film formed.
The present invention is intended to solve the conventional problem described above, and the object is to provide a facing-targets sputtering apparatus which is able to prevent reaction plasma from intruding toward the target and to prevent the generation of arc discharge during the sputtering operation, wherein the manufactured thin film is free from damage due to plasma, and uniform in its in-plane distribution.